Inkjet printing technology has become widely known and is often implemented using a thermal ink propulsion mechanism. Such technology forms characters and images on a medium, such as paper, by expelling drops of ink in a controlled fashion so that the drops land on the medium. In its simplest form, the printer can be understood as a working combination of a mechanism for moving and placing the medium in a position such that the ink drops can be placed on the medium, a print cartridge which controls the flow of ink and selectively expels drops of ink to the medium, and appropriate controlling hardware and software to position the medium and expel droplets so that a desired graphic is formed on the medium.
A conventional print cartridge for an inkjet printer comprises an ink containment device and an ink ejection assembly which selectively heats and expels ink drops in a controlled fashion. An alternative ink ejection apparatus for other than thermal inkjet printers uses mechanical propulsion techniques such as piezo-electric drivers to impart momentum to the ink. For thermal inkjet printers, the ink ejection assembly typically includes a laminate structure comprising a semiconductor or insulator substrate capped with a plate or surface permeated by orifices or nozzles arranged in a pattern beneficial to the deposition of ink on a medium. In thermal inkjet printers, the heating and expulsion mechanism consists of a plurality of heater resistors formed on the semiconductor, each heater resistor associated with one of the nozzles in the nozzle plate. Each of the heater resistors is coupled to the controlling hardware and software of the printer such that each of the resistors may be independently energized to quickly vaporize a portion of ink and expel a drop of ink from the nozzle. Ink is stored in an ink reservoir in the print cartridge, in most implementations, and is typically loaded into a firing chamber which is disposed about the heater resistor. The pressure created following the ink expulsion causes ink to be removed from the ink reservoir through ink manifolds and ink conduits and into the ink firing chambers.
Currently, the most widely used thermal inkjet printers utilize a relatively small printhead (approximately 5 mm.times.10 mm) that is mounted on a protruding "nose" of the ink cartridge, thereby being positioned in close proximity to the medium to be printed upon. Such an arrangement is shown diagrammatically in FIG. 1A. Here, a cross section of the nose of the cartridge body 101 shows a printhead 103 affixed to the body 101 in a well 105 having a depth that is approximately equal to the thickness of the printhead 103. A flexible electronics circuit commonly known as a tape automated bonding (TAB) circuit 107 is conventionally affixed to that portion of the body 101 which is directly opposite the medium to be printed upon. The TAB circuit 107 is typically wrapped around one of the other surfaces of the nose so that an electrical connection may be made to the other controlling portions of the printer. This is illustrated diagrammatically with point contact 109. Electrical connection between the TAB circuit 107 and the printhead 103 is typically made using a beam lead technology (as illustrated with beam lead 111) but may also be accomplished with wire bonding techniques. In order to prevent electrical shorts due to ink and to provide mechanical protection, an encapsulating substance (not shown) is typically placed over the wire bonding or beam lead area. Ink is provided to the printhead from a reservoir of ink by ink ducts 113 within the print cartridge.
An alternative arrangement which has come into recent use is illustrated in FIG. 1B. This arrangement utilizes the TAB circuit 107' as an nozzle plate as well as it conventional electrical interconnect purpose. The nozzles are laser ablated or otherwise created in the flexible polymer TAB circuit tape and the TAB circuit is stretched over the remainder of the printhead 103' in such a way that ink is ejected from the TAB circuit nozzles. As described relative to FIG. 1A, the TAB circuit is wrapped around the side of the body 101 and electrical connection is made by way of a contact 109. Ink is brought to the printhead 103' by ink ducts 113 in the print cartridge.
These techniques have demonstrably proven their value in many successful products. The extension of these technologies to a print cartridge which is expected to print a wide print swath, perhaps the width of an entire medium page, exposes problems which require solutions before these technologies can be used for a wide area print cartridge.
If one desires to create a print cartridge which is capable of printing a wide swath in a single pass (for example a 5 cm to 20+ cm swath), or as much as a 20 cm swath, a large number of printing nozzles must be positioned near the medium to be printed upon. It is conceivable that a printhead having thousands of nozzles could be so positioned, but the reliable fabrication of such a large number of nozzles in a single printhead is not economically feasible. Accordingly, a smaller number of nozzles in an ejecting mechanism can be economically produced and a plurality of these ejection mechanisms can be ganged together in a single printhead to effectively obtain a large number of nozzles. Coordinating such a plurality of ink ejection devices requires a high degree of registration of nozzles of separate ink ejectors as well as a high degree of planarity between the ejecting surfaces of the ink ejectors so that the drops ejected from one ink ejector are properly placed on the medium relative to the drops ejected from another ink ejector.
Accordingly, it is desirable to create a printhead employing a plurality of ink ejection apparatus in a wide array configuration. Such an array should provide a reliable fluidic and electrical interconnect between the print head and the plurality of ink ejection apparatus as well as a high degree of registration between the ink ejection apparatus with a corresponding reduction of misplaced ink drops.